Aging out of allergies

Julie Deardorff, Tribune Newspapers

Two years after outgrowing a peanut allergy, Holly Sweenie finally took a peanut butter and jelly sandwich to school. "It took me a long time to get up the courage to pack one," said Sweenie's mom, Susan, of Canton, Mass. "I assumed allergies were something she'd always have."

Happily, allergies aren't always life sentences. But it can be difficult to tell when children have aged out of an allergy, and if they have, whether eating those previously forbidden foods should be part of the treatment.

A whopping 80 percent of children will lose their sensitivity to milk, egg, wheat and soy allergies by adulthood, said Dr. Robert Wood, director of pediatric allergy and immunology at Johns Hopkins Children's Center and a prolific allergy researcher. Though less common, even life-threatening peanut and tree nut allergies can recede; over time, 20 percent of children will lose their sensitivity to peanuts and 10 percent will be able to tolerate tree nuts.

Some children with respiratory allergies such as seasonal allergic rhinitis (hay fever), meanwhile, can improve and even "outgrow" the allergy as they mature, usually around puberty, said Dr. Michael Welch, co-director of the Allergy and Asthma Medical Group and Research Center in San Diego. "Often, the skin test reactivity stays the same, but the symptoms of a sizable number of children greatly improve with age," he said.

Still, allergy rates continue to rise — they've doubled since the 1970s — and defy explanation. Though some people have a genetic predisposition, scientists don't know what causes allergies or why children can overcome sensitivity to certain foods but not others. Nor do they know why some children have no hay fever during their preteen years, but develop it when they hit adolescence.

Treatment generally involves avoidance; the hope is that the immune system will gradually forget about the allergen. But paradoxically, "exposure may help someone with allergies become more tolerant of small amounts," said Wood.

For patients with environmental allergies, allergy pills or shots, also called immunotherapy, are used to help with desensitization. It's thought that immunotherapy gradually retrains the immune system to completely disregard or tolerate the allergens that cause the reactions.

For food allergies, however, immunotherapy isn't quite ready for prime time. Preliminary data show that giving children with milk allergies increasingly high doses of milk over time may ease or help them overcome the allergy, but researchers warn it should never be tried at home. Feeding peanuts to someone with peanut allergies, for example, can result in life-threatening anaphylactic shock.

If a child has outgrown the peanut allergy, it may be a different story. Some research shows reintroducing peanuts after a child can tolerate them may help prevent a recurrence. Though the mechanism isn't known, Wood's work has shown children who outgrew peanut allergies and then ate peanut butter, shelled peanuts or peanut candy at least once a month had a lower risk of recurrence than those who didn't.

Still, Wood recommends that children who do eat concentrated peanut products carry epinephrine injections for at least a year after passing a food challenge, an allergy test in which the child eats small amounts of the suspected allergen in the doctor's office.

Holly Sweenie was 2 years old when she was diagnosed with peanut, milk and egg allergies. "The toughest part was the meal preparation and sending her off to school," said Susan Sweenie. "As much as you try to prepare for things — like baking our own cupcakes for school parties — you never know what can happen." Also, due to the multiple allergens, "it was tough getting protein into her, so we relied on soy milk and lots of lean meats, which is never what a kid really wants."

But one day Sweenie accidentally gave Holly a baked good containing eggs. When she had no reaction, she was retested; the results showed she had outgrown both the egg and milk allergy, which was the most severe. A year later, by the time she was 5, tests showed she had outgrown the peanut allergy too.

For the first two years, Susan Sweeny was extremely nervous about giving Holly peanuts. But today, she's no longer anxious about sending her daughter off to school with a peanut butter and jelly sandwich and a yogurt.

Onset: 1 to 2 years old. Exceptions: Fish and shellfish allergies tend to emerge in adulthood.

Treatment: Avoidance. Allergies are monitored with skin or blood tests. If a child appears to become less allergic over time, a food challenge can be given. This can involve making extracts with the food and pricking the skin to see how much the skin reacts. In some cases, as with egg and milk allergies, children can be given a baked version of the food. If there's no reaction, it may be "reasonable to gradually introduce it at home," said allergy researcher Dr. Robert Wood.

Who may outgrow? About 50 percent of children outgrow milk and egg allergies by age 10; however, if a child has severe eczema, they are less likely to outgrow their milk or egg allergy, according to new research. About 50 percent of children outgrow soy and wheat allergies by age 6. Overall, 80 percent of milk, egg, soy and wheat allergies are eventually outgrown, but it seems to be happening more slowly than it used to. Children are more likely to outgrow a peanut allergy if they have low levels of peanut-specific IgE, the antibodies produced by the immune system that cause allergic reactions, according to Wood's research. These antibodies can be measured with a widely available blood test.

ENVIRONMENTAL ALLERGIES

Dust mites, trees, grasses, weeds and molds

Onset: Age 2 or 3. Though less common, it's possible to develop allergies later in life.

Treatment: Avoidance and immunotherapy. Though injections (allergy shots) have traditionally been used, immunotherapy given as pills or drops under the tongue is also effective, according to a Cochrane Systematic Review.

Who may outgrow? Those who do will likely do so around puberty. A higher proportion of boys seem to outgrow environmental allergies; it may be a hormonal influence, said Wood. In younger children, asthma, allergic rhinitis and respiratory allergies are twice as common in boys than girls. But in adolescents and adults, they're more common in females. The majority of children outgrow bee-sting allergies; for those who don't, allergy shots (venom immunotherapy) can reduce risks.